Interesting to see some people feel a difference in their thumbs.
I'm right handed, and never ever though of that while using the hardware keyboard of my Motorola Photon Q, which have the cursor on the right side. I find it comfortable to edit text, and it has the advantage of being on the same side as the backspace key which is also used when editing text (moving the cursor backward, delete some characters, move forward, etc...).
I wouldn't used it as a gamepad to play games, not so much because we have the habit of having it on the left side on gamepads, but because it is too small and needs too much pressure to be used comfortably and fast in games. This is a completely different usage as when used in typing and editing.

chenliangchen, I would recommand for the pressure needed to activate the key to stay below the levels needed for the Photon Q, as it is the limit to be comfortable. On long typing sessions, it starts to feel heavy.
Good luck with your project, the moto Z is too big for me, but I will follow your work closely !